000
AXPZ20 KNHC 280921
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED JUL 28 2010

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...

ITCZ AXIS ALONG 10N86W TO 12N103W TO 11N115W TO 08N126W TO 
10N131W TO 09N135W TO 09N140W. SCATTERED MODERATE TO STRONG 
CONVECTION IS WITHIN 180 NM S OF THE AXIS BETWEEN 84W AND 90W. 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 60 
NM EITHER SIDE OF THE AXIS BETWEEN 94W AND 97W.

...DISCUSSION...

AN UPPER LEVEL TROUGH EXTENDS FROM WELL N OF THE DISCUSSION AREA 
THROUGH 32N130W AND SW TO 23N137W. THE TROUGH IS BECOMING 
SHEARED IN THE FACE OF A BROAD UPPER RIDGE WHICH EXTENDS FROM AN 
ANTICYCLONE POSITIONED ALONG THE W COAST OF BAJA CALIFORNIA NEAR 
25N116W W-SW TO 21N133W. THE TROUGH IS EXPECTED TO GRADUALLY 
RETROGRADE TO THE W AS THE BAJA CALIFORNIA RIDGE BUILDS WESTWARD 
DURING THE NEXT FEW DAYS. VERY DRY AND STABLE AIR DUE TO 
MODERATE TO STRONG SUBSIDENCE IS NOTED NW OF A LINE FROM CENTRAL 
BAJA CALIFORNIA NEAR THE ANTICYCLONE CENTER TO 15N140W. 

MID TO UPPER LEVEL MOISTURE IS BEING ADVECTED WESTWARD ACROSS 
THE MAJORITY OF THE REMAINDER OF THE DISCUSSION AREA SE-S OF THE 
AFOREMENTIONED LINE BY THE ANTICYCLONE NOTED ABOVE BY QUASI 
ZONAL EASTERLY FLOW ALOFT. A LACK OF LOW LEVEL FORCING OUTSIDE 
OF THE ITCZ IS HINDERING THE DEVELOPMENT OF DEEP CONVECTION W OF 
97W. DIURNALLY ENHANCED CONVECTION OVER CENTRAL AMERICA HAS 
SHIFTED OFFSHORE INTO THE E PACIFIC AND REMAINS CONFINED E OF 
90W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION EXISTS N 
OF 03N WITHIN 120 NM OF THE COAST OF COLOMBIA...WITH SCATTERED 
MODERATE TO STRONG CONVECTION WITHIN 120 NM OF THE COAST OF 
MEXICO BETWEEN BETWEEN 100W AND 104W.

AT THE SURFACE...BROAD 1028 MB HIGH PRES IS CENTERED WELL NW-N 
OF AREA NEAR 44N141W WITH AN ASSOCIATED RIDGE AXIS EXTENDING SE 
THROUGH 32N138W TO 22N112W. A WEAK SURFACE TROUGH IS JUST N OF 
THE ITCZ EXTENDING FROM 17N111W TO 13N118W WITH ONLY SCATTERED 
SHOWERS NOTED WITH IT. GLOBAL MODEL GUIDANCE CONTINUES TO 
DEVELOP AN AREA OF LOW PRES ALONG THIS TROUGH BEYOND 48 HOURS 
WITH EACH MODEL SOLUTION VARYING IN THE STRENGTH.

ANOTHER WEAK TROUGH IS EMBEDDED IN THE ITCZ EXTENDING FROM 
14N132W TO 07N134W. AN EARLIER FLARE UP OF CONVECTION HAS 
DISSIPATED AND THIS TROUGH WILL SHIFT W OF THE AREA BY 24-48 
HOURS.

FRESH NW WINDS OF 20 KT WILL RETURN BY 18 HOURS WITHIN 120 NM OF 
THE W COAST OF BAJA CALIFORNIA FROM 24N TO 29N THEN WILL PERSIST 
TO 20 KT THROUGH 48 HOURS WITH THE MOST PRONOUNCED WINDS 
OCCURRING FOLLOWING PEAK AFTERNOON HEATING.

OTHERWISE FRESH E-SE WINDS OVER THE SE PACIFIC CONTINUE TO 
GENERATE LONG PERIOD SOUTHERLY CROSS EQUATORIAL SWELL UP TO 9 FT 
ENCROACHING INTO THE DISCUSSION AREA WATERS S OF 10N-12N AND W 
OF 80W. THESE SEAS WILL PERSIST DURING THE NEXT 48 HOURS.

$$
LEWITSKY